JBL Woofer Questions. Education badly needed.

[ivica]

Hi Greg; Q1,

Are two woofers better than one? Hell yeah! If ones good, two's got to be better right? ........ Cut the required excursion and you cut the distortion. Q1a, Will two 12's "bring it" better than one 15"? Depends on what bring it means to you.
To me? I like well controlled drivers so if you compare apples to apples,,. Lets use 2206's, 2226's and 2241's here, the common part of these transducers is the motor assemblies, they are identical. If you do the math a pair of 15's have about 63 more inches of cone area than a single 18, and fully twice the motor force power. Which do you think will have more punch, or pop, or snap? ........

Q3, Two woofers in one cabinet, separated or not?
For me this depends on how high you are going to use them. You need not worry about standing waves until the enclosure becomes acoustically large ie one half a wavelength at the highest frequency of interest. A sub enclosure crossed out at 80Hz needs no thought given to its internal dimensions until one of them reaches right about seven feet. This is a very nice gift from the science of small room acoustics, a degree of design freedom that is rare indeed in the world of acoustics. The problem comes at you fast however as at 1000Hz you only get about 6.75" so at some point you are going to have to deal with internal resonances. If I am going to run a pair of woofers up fairly high, I split the box with a divider, no ports,......

On the cabinet size vs driver thing, yeah you can put a driver like a 2241 in an oversize box and port tune it low and EQ it flat, but I have never been able to get them to sound really good doing that, that why JBL made 2245's. It has become apparent to me through much, much, much trial and testing that the more you have to force a design, the harder it is to get great sound form it. Use the right drivers for the job. I am all about taking the path that leads to knowledge. When you step out and do, you gain knowledge and experience and that first hand knowledge is power. But realize this, that even though you can surely figure this all out on your own, a good deal of time can be saved by searching and understanding successful designs that already exist. JBL has done a lot of this homework for you. Oh yeah, never listen to anyone on the internet! Barry.

Hi Barry,

Very nice explanation.

Here I want to add just a few words, from my personal experience.
Putting two bass drivers instead of one would not change too much the sound character of the driver. I have recognized that comparing 4333 and 4355 (DIY) boxes. Yes 4355 can work 'more reluctantly' but the LF character remain, in comparison to the 4345. I prefer the 4345 LF more then 4355/4333.
So your words:"..Use the right drivers for the job..." can be the leading idea. I believe that at JBL they have spent a lot of time in modeling and experimenting, but some time 'marketing dept.' did the final decision.
( I believe that was the reason that something like 2245+2202+2441+2405 never come together),
not to mention here that some newer design priced in several "tens of thousand of $" would need SUB-WOOFER (??!!??).

Other thing: "..you can put a driver like a 2241 in an oversize box and port tune it low and EQ it flat, but I have never been able to get them to sound really good doing that, that why JBL made 2245's...." .I have understood as: 'Applied electronic EQ would never enhance the driver sound character'. If that is not the truth, it would be easy to make much cheaper speaker incorporating today cheap DSP embedded into the speaker-amplifier combo, that would be perfectly flat FR. Such "ideas" had been done in the "history" (not to mention feed-back controlled combos).

Reagrds
ivica

[Robh3606]

If box volume is really an issue KIS and use a single. Everest and the 4435 are both 2 1/2 ways with both woofers used as a pair over a very limited bandwith. Dual woofers operating over the same range are great for max SPL and power handling like in SR and Cinema applications . What are you trying to acomplish??

Rob

[cgregory4]

Hi Greg;

I have been around this topic a bit and here's my take, while I listen to a pair of 4435's I might add.

I am all about taking the path that leads to knowledge. When you step out and do, you gain knowledge and experience and that first hand knowledge is power. But realize this, that even though you can surely figure this all out on your own, a good deal of time can be saved by searching and understanding successful designs that already exist. JBL has done a lot of this homework for you.

Oh yeah, never listen to anyone on the internet!

Barry.

Wow! What a breath of fresh air! Finally ... Something an old guy can understand! Thank you! Stick a fork in me ... I'm done.

You addressed every single one of my questions, and gave me some great advice -- to boot!

Willie and Ivica: I very much appreciate your taking time to respond, as well. You've both given me things to ponder -- a good thing for an old brain that needs exercise!

The wife hates, but tolerates, my audio obsession. BUT, she's going to Greece with the mother-in-law for several weeks! I feel a 'project' coming on!

Greg

[tomee]

Not to worry. I 'rescued' 6 4425s out of New York and paid outrageous shipping to have them sent to Texas. They were going to be 'parted out'. I saved them. I'm one of the 'good guys' who will pay to save a speaker!

my apologies for assuming otherwise! I read in a different post about you once having 4425s, then only boxes in this one...and I jumped to the wrong conclusion. my bad, as the kids say

The woofer surrounds were completely gone. I'm in the process of paying to have all the 2214Hs fixed. The tweeters I've tested have been OK, but really dirty. The cabinets -- I'm refinishing.

Your second paragraph may be the 'clincher', and I may come to the same conclusion. BUT, the fact that no one has directly addressed in any detail all 3 of my questions, makes me think that maybe not many LH members have pondered something like your statement, "The 2 14"ers will have more cone area than a single 15 - maybe about the same as single 18 - BUT that doesn't mean it will work better than a single 18." BUT, what if it does? The only way to find out is to try. However, at the end of the day, I do agree the JBL folks were absolutely without equal, wrt design and build. However, I also think that in the 60s and 70s they were a lot more open to various combinations than we seem to be today -- both in their 'custom' speaker enhancements and their 'kits', as well.

I hate that I got sucked into this JBL vortex! Different drivers with different horns with different adapters with different voice coils with different cones with different frequency dividers with different dome materials with different .............!!!!!!!!!!!!!!!!!

But, as you can see it doesn't bother me ...............bother me...................bother me.................bother me.

Greg

I totally understand about being sucked into the JBL vortex!! So many systems, and components, and so many for sale on ebay etc.. the project ideas are endless! It sounds like you have a good start on the 4425s, but maybe you're wondering what happens if you double them up? I think a pair of 4425s mounted side-by-side, with one of the horns removed, would make a decent 'mini-4435' type system. The cabinet with the horn removed would need a blank plate in its place, and the crossover for the 2nd woofer would need to be modified to allow only signal from 150Hz or lower (what did the 4435 use??).

maybe something in here has a clue.. I can't seem to find a reference to the 'helper' woofer crossover...
http://www.audioheritage.org/html/pr...bl/4430-35.htm
http://www.jblproservice.com/pdf/Stu...ies/4435LR.pdf


The pair of 12's would have slightly more cone area than a single 2235, but the xmax is lower so max SPL would be lower than a 2235. (..and although 2 LE14s are about the same area as a 2245, xmax is almost double for the 2245..so it wins! this was the argument put to me some time ago for why sometimes a single large woofer is better than 2 smaller ones. Sometimes, if the design is right, the larger frame can allow for a very high xmax...and I think the 2245 is one of those 'special' designs! )

(in case you haven't seen it, see here for cone area, xmax etc.
(http://www.jblproservice.com/pdf/thi...parameters.pdf )

and see figure 13 here to see measurements on what the dual woofers does for the 4435 vs the 4430
http://www.xlrtechs.com/dbkeele.com/...er Systems.pdf

anyway, have fun restoring those 4425s! maybe put up some pictures of them if you can, as the work progresses?